Automatic thermometer calibration system

ABSTRACT

A system for automatically calibrating and classifying measuring instruments such as mercury clinical thermometers, by accurately determining the distance between two reference points established by two known reference parameters. The detection of the reference points is made by scanning a laser beam over the mercury column and detecting the change in the reflection characteristic of the beam at the upper level of the column.

United States Patent 51 3,678,729 Geis et al. 1 July 25, 1972 s41AUTOMATIC THERMOMETER 3,316,076 4/1967 Blackman ..73/1 F CALIBRATIONSYSTEM 3,377,837 4/1968 Ayres ..73/1 F [72] Inventors: James D. Gels,Cheshire; John H. Troll,

Ridgefield; Harry Gluz, South Norwalk; 1 Cole H. Baker, Stratford, allOf Conn. Clemem Swisher Attorney-Sandoc, Hopgood and Calimafde [73]Assignee: Iris Corporation, I-lamden, Conn.

, [22] Filed: Aug. 3, 1970 '21 Appl. No.2 60,596 [57] ABSTRACT A systemfor automatically calibrating and classifying measuring instruments suchas mercury clinical thermometers, by ac- CCll. curately determining thedistance between two reference [58] Field 73/1 F points established bytwo known reference parameters. The detection of the reference points ismade y scanning a laser [56] References Cited beam over the mercurycolumn and detecting the change in the reflection characteristic of thebeam at the upper level of I UNITED STATES PATENTS the column.

3,5 85,839 6/1971 Bollinger ..73/l F 13 Claims, 11 Drawing Figures 1. AS 6 Z! //fl (ab/7W0! 05756701? LOG/C 32 x flV/ EP sea/v 24a Mara/a aCJNT ML SCAN Moro/2 I4 Patented July 25, 1972 7 Sheets-Sheet 2 NQI 5 w a0 z Maw e r V n 5 5 Y 4 ENRE Patented July 25, 1972 7 Sheets-Sheet 5FIG. 3 F IG. 4

JAMES W555? BY J m zg dzw 4 TfOR/VEKS' 1 AUTOMATIC THERMOMETERCALIBRATION SYSTEM The present invention relates generally to instrumentcalibration, and more particularly to a system for automaticallycalibrating and classifying measuring instruments such as mercurythermometers, and the like.

Measuring instruments such as clinical thermometers are commonly of thetypes employing a medium such as mercury, which rises within a narrowtube or capillary by an amount proportional to the value of a sensedexternal parameter, such as temperature.

In a clinical thermometer, a quantity of mercury is contained in areservoir formed in a bulb at the lower end of the instrument. Thereservoir communicates with the lower end of a narrow capillary boreformed in a transparent thermometer casing made of a suitable materialsuch as glass or plastic. The extent to which the mercury rises in thecapillary bore is proportional to the level of the measured temperature.When the thermometer is removed from the location at which thetemperature measurement is made, the mercury in the capillary boreremains substantially at the level to which it was raised until thethermometer is vigorously shaken to thereby return the mercury column toits normal position.

The amount by which the mercury is raised along the axial dimension ofthe capillary bore in response to the measured temperature is afunction, as noted above, of the level of that temperature, but is alsoproportional to the volume of mercury contained in the instrument aswell as the volume of the bulb reservoir and the capillary. The latterfactors are determined at the time the thermometer is manufactured.There are, however, minor variations introduced during the manufacturing process between different thermometers with respect to theircapillary bore and bulb volumes, as well as the volume of mercuryintroduced into the instrument.

As a result of these variations in the critical thermometer dimensions,each thermometer must be separately calibrated to ensure uniformreadings on all thermometers when exposed to corresponding externaltemperatures for measurement.

Heretofore, calibration of thermometers has been performed by immersingthe initially uncalibrated thermometer into solutions or bathsmaintained at two reference temperatures, such as 98 F and 106 F. Anoperator supplied with an ink marking device draws a line or ink mark atthe termination or discontinuity of the mercury column within thecapillary bore established in response to both the lower. and higher ofthe reference temperatures.

The distance between the two reference markings is measured and thethermometer is then categorized into one of a plurality of classes incorrespondence to the distance between the markings. Thermometersfalling in each class are thereafter calibrated by printing on them agraduated scale of temperatures, a different scale being provided foreach class of thermometers. Thermometers in which the distance betweenthe reference points falls outside the established classes are rejectedas being unacceptable for use.

It will be appreciated that the presently employed procedures forthermometer calibration largely involve a series of manual operations,and are thus to a large extent nonautomatic in nature. That conventionalprocedure is relatively tedious, slow and imprecise. The need to trainunskilled personnel to perform this task is also time-consuming andexpensive, thus adding to the manufacturing cost and the ultimate costto the customer.

Attempts have been made to automate the thermometer calibratingprocedures in a practical and economical manner while still ensuringrepeatability, accuracy, and rapid, reliable and low-cost operation.These attempts have, however, been by and large unsuccessful since noeffective way has yet been developed to accurately determine the upperlevel of the mercury column established by the reference temperatures.For this reason, the instrument industry continues to employ the slowand tedious manual operations for calibrating mercury clinicalthermometers as well as similar measuring instruments, such asbarometers, and the like.

It is thus an object of the invention to provide an improved system forautomatically calibrating measuring instruments, such as mercurythermometers and the like.

It is another object of the invention to provide an improved system forautomatically classifying instruments such as mercury thermometers as afunction to the response of the instrument to a set of referenceparameters.

It is a further object of the invention to provide a system of the typedescribed which is capable of calibrating large numbers of instrumentsin a continuous, substantially automatic, and yet reliable andhigh-speed manner.

It is still another object of the invention to provide an automaticinstrument calibrating and classifying system in which laser, optical,analog, and digital techniques are employed to provide increasedaccuracy of calibration.

In the instrument calibration system of the invention, which is hereinspecifically disclosed for purposes of example, as a system for theautomatic calibration of mercury clinical thermometers, the instrument(thermometer) is subjected to a first reference temperature after whichthe resulting level of the mercury column is detected. The instrument isthen transported to a station at which it is exposed to a secondreference temperature and the resulting level of the mercury column isagain detected. The distance between the two detected reference levelsis sensed and utilized to classify the thermometer into one of aplurality of categories.

In accord with one aspect of the invention, the level of the mercurycolumn is accurately determined by means of sensing the change in thereflection characteristics of a laser beam from the mercury column thatoccurs at the meniscus of the column. It has been determined that thereflection of the laser beam from the mercury-containing section or fromthe section of the column containing no mercury is mostly horizontalalthough of significantly differing intensities; the intensity from themercury containing portion being of the greater intensity. However, whenthe laser beam is directed at the concave meniscus formed at the uppersurface of the mercury column, the reflection characteristic of the beamsuddenly and sharply changes to a generally vertical orientation.

In the embodiment of the invention herein described, a first laser beamis caused to scan over the :mercury column after the thermometer isexposed to the first reference temperature. When the characteristicchange in the reflection from the upper surface of the mercury column isdetected, the scanning of the beam is interrupted and an inkingmechanism is actuated to apply a mark on the thermometer at the upperlevel of the mercury column to thereby establish a first reference line.

The thus marked thermometer is then moved to a second station at anelevated controlled temperature. The mercury column there rises to asecond elevated level which is detected by the scanning of a second'laser beam over the mercury column much in the same manner as in thefirst scanning and inking station. Means are provided at the secondscanning station to produce a signal proportional to the distancebetween the upper level of the elevated mercury column and thepreviously inked line,

That distance signal is converted to a binary classification signalwhich is processed at an unloading and classification station along withan indexing signal representing the indexed position of the thermometer,to cause the automatic release of the thermometer into a particularreceptacle corresponding to the thermometer classification.

To the accomplishment of the above and to such further objects as mayhereinafter appear, the present invention relates to an automaticthermometer calibrating system substantially as defined in the appendedclaims and as described in the following detailed description of theinvention taken together with the accompanying drawings in which:

FIG. 1 is a schematic diagram illustrating the means by which the upperlevel of a mercury column in a measuring instrument is detected asemployed in the system of the present invention;

FIG. 2 is a side elevation of the calibrating and classifying station ofthe system of the invention;

FIG. 3 is an elevation in schematic form of the first scanning andcalibration station of the system of the invention, viewed in thedirection of the arrows 3-3 in FIG. 2;

FIG. 4 is a view similar to FIG. 3 of the second scanning andtemperature calibration station of the system as viewed in the directionof the arrows 4-4 in FIG. 2;

FIG. 5 is an elevation view in schematic form of the instrumentunloading and sorting station of the system;

FIG. 6 is an elevation view of the thermometer release mechanismemployed at the unloading station of the system;

FIG. 7 is a top plan view on an enlarged scale, illustrating the mannerin which the instruments are retained and released from the conveyor;

FIG. 8 is a schematic diagram in block form illustrating the beamscanning and inking control circuitry and the first scanning station;

FIG. 9 is a corresponding schematic block diagram of the logic anddigitizing circuitry associated with the second scanning station of thesystem;

FIG. 10 is a schematic logic diagram of the instrument sorting sectionof the system; and

FIG. 11 is a view in schematic form similar to FIG. 1 of an alternateembodiment of the invention.

The calibrating and classifying system of the present invention isherein specifically illustrated with reference to the automaticcalibration of a clinical thermometer of the type commonly used tomeasure the temperature of a patient. A thermometer of this type isgenerally made of a transparent body or casing in which a bulb is formedat the lower end. A capillary bore is formed within the interior of thecasing and a quantity of a suitable medium, most often mercury, isplaced in the bulb and rises partially up the axial length of thecapillary bore. As is known, the height to which the mercury rises inthe capillary bore is a function of the temperature to which the bulb isexposed, so that the upper surface level of the mercury in thecapillary, at which a concave meniscus is formed as a result ofcapillary action, provides a direct indication of that temperature.

As described above, to convert the height of the mercury within thecapillary bore into a meaningful and accurate indication of temperatureit is necessary to calibrate the thermometer at the time of itsfabrication so that a numerical indication, such as the normal bodytemperature reading of 98.6 F, may be assigned to a particular height ofthe mercury column of a particular thermometer.

The system of the invention is directed to the automatic calibration ofsuch thermometers and similar instruments, as well as to the automaticsegregation or classification of thermometers at the time of theirmanufacture based on the distance between two levels of the mercurycolumn established in response to two accurately controlled referencetemperatures to which the instrument is exposed. Thermometers in whichthe distance between the two detected levels are greater or less than apredetermined value are automatically rejected.

In accordance with one aspect of the invention, the calibration of theinstrument includes the detection of the upper level of the mercurycolumn by scanning, as shown in FIG. 1, a narrow light beam, such asthat produced by a laser 10, over a mercury column 12 extending upwardlyfrom a bulb portion 14 formed at the lower end of a thermometer 16. Ithas been found that the reflection characteristics of the laser beamfrom the thermometer differ in accordance with the portion of themercury column on which the beam is incident. More particularly, it hasbeen found that the reflection of a laser beam from either the sectionof the capillary bore containing mercury or in the section of the borein which there is no mercury, is generally horizontal. However, as thebeam is scanned across the upper level of the mercury column, themeniscus formed thereat as a result of capillary action, causes thegeneration of a sharply, unique vertical reflection. The sensing of thissharp change in the reflection characteristic of the laser beam at themeniscus of the mercury column permits the detection of the upper levelof the mercury column in a highly precise manner,

in the order of accuracy of .0001 inch or better if beam shapingtechniques are employed to narrow the width of the laser beam.

As is shown schematically in FIG. 1, the beam from laser 10 is caused tobe incident on a mirror 18 and reflected from there onto the mercurycolumn 12, which has risen to a height corresponding to the presettemperature of a reference temperature solution or bath 20 in which thebulb 14 of the thermometer is immersed. The laser beam is caused to scanvertically over the column by the operation of a step motor 22 coupledto mirror 18 by suitable mechanical means generally indicated 24. Adetector or detector array 26 moved along with the scanning mirror 18,receives'the beam reflected from the mercury column. Detector 26 iscoupled to logic circuitry 28, described in greater detail below withrespect to FIG. 8, which in turn is coupled to a scan motor controlcircuit 30. The latter in turn is coupled to motor 22 and to an inker 32which is also mechanically coupled to motor 22 and moves along withmirror 18.

When detector 26 detects the unique reflection characteristiccorresponding to the scanning of the laser beam over the upper level ofthe mercury column, it produces a signal which is processed in logiccircuit 28 to produce at motor control 30 a disabling signal for motor22 and an enabling signal for inker 32. As a result, scanning of thebeam over the mercury column is temporarily halted and an ink line isprinted on the thermometer casing at the level of the meniscus. The linethus formed accurately represents the height to which the mercury columnhas risen in response to the temperature of controlled temperaturesolution 20.

GENERAL SYSTEM ORGANIZATION In the system of the invention, as shown inits complete form in FIG. 2, a plurality of instruments here shown asthermometers are secured, by means more completely described withreference to FIG. 7, to the upper flight of a chain conveyor 34 at aloading and control station A. Conveyor 34 is incremcn tally drivenbetween loading station A and an unloading and classifying station B bymeans of a sprocket wheel driven by a drive motor controlled from aswitching and speed control panel 36 located at station A. The conveyor34 passes over rollers 38 mounted at the loading end of the conveyor ona longitudinal support member 40. The latter is supported by a series ofspaced vertical feet 42 which are in turn connected at their lower endsby a longitudinal strut 44. The thermometers loaded onto the upperflight of the conveyor belt at station A are incrementally moved over apair of idlers 46 and 48, which urge the conveyor into a downwardlyinclining path 50. Path 50 terminates at its lower end in a controlledtemperature solution or bath 52 located at a first reference temperaturestation C. The temperature of bath 52 is kept substantially constant ata predetermined temperature, e. g. 98 F, by means of a temperaturecontrol system 54, the design of which is well known in the art and thusnot further described herein.

During its travel through bath 52, the mercury level in each of thethermometers is raised to a first reference level in response to thattemperature. This rise, as noted above, is a function of the volume ofmercury in each thermometer as well as the volume of mercury in the bulband the volume of the capillary bore. Since there are variations in oneor all of these factors in the thermometers, there will be correspondingvariations in the levels to which the mercury rises in response to thetemperature in bath 52.

The thermometers are then moved incrementally over an upwardly inclinedpath 56 established by idler rollers 58 and 60 to remove thethermometers from bath 52 and transfer them into a scanning and inkingstation D, which corresponds to the apparatus shown schematically inFIG. 1.

In station D, a beam from laser 62 (laser 10 in FIG. I), suitablymounted on the conveyor support, is sequentially and vertically scannedover the mercury columns in the thermometers passing through thestation. When the characteristic reflection at the top of the mercurycolumn is detected by the detector, a solenoid or the like is operatedin a manner more completely described below to cause an ink marker toapply an ink line to each of the thermometers at the upper level oftheir respective mercury columns, to thereby establish a first 98 Freference line on each of the thermometers.

The thermometers are then sequentially and incrementally transferred outof station D down an inclined path 64 formed by idler rollers 66 and 68,and are then passed into a second controlled temperature bath 70 locatedat a second reference temperature station E. A temperature higher thanthe temperature at station C, such as 106 F, is established andprecisely controlled in bath 70 by a temperature control system 72,which may be similar to control system 54 at station C. Upon enteringthe controlled temperature bath 70, the mercury levels in thethermometers rise to a second reference level above that established anddetected at stations C and D respectively. I

The thermometers are then removed from bath 70 along an upward incline74 formed by rollers 76 and 68, and arethereafter incrementallytransferred to a second scanning station F at which a beam from a secondlaser 80 is caused to sequentially and vertically scan over the mercurycolumns in the thermometers. As described more completely below withrespect to the description of FIG. 4, the laser beam is scanneddownwardly along the thermometer until the unique reflectioncharacteristic at the upper meniscus of the mercury column is detected.The laser beam then continues to scan down the mercury column until itdetects the ink line which was previously applied at laser scanningstation D. A shaft encoder mechanically coupled to the scanning memberproduces a series of output pulses the number of which is proportionalto the distance scanned between the two temperature reference levels;that is, the levels to which the mercury column rose in response to thetemperatures of the two reference temperature stations.

The thermometers are then incrementally transferred out from the secondscanning station F over an idler roller 82 and into the unloading andsorting station B, from which the thermometers are selectively removedfrom the conveyor belt and dropped into one of a preselected number ofreceptacles or bins corresponding to the measured distance between thetwo reference levels. That is, the position of thermometer release is afunction of the number of pulses produced by the shaft oncoder at thesecond scanning station. As herein described, the encoder pulses areconverted into a digital code or number corresponding to the categorythat the thermometer is placed in accordance with the measured distance.The thermometers are thus automatically calibrated and classifiedaccording to their response to the two reference temperatures.

The thermometers received in each of the classification bins are thenprinted or stamped with a graduated scale between the two referencetemperatures in a known manner, to form the finished thennometer, adifferent scale being imprinted on different categories of thethermometers. Those thermometers in which the distance between the tworeference levels falls either above or below a preselected value arerejected as being unsuitable for use.

The conveyor belt passes over rollers 84 at the unloading station andthen travels over return rollers 86 at the lower flight of the conveyoruntil it returns to the upper flight and loading station A, where itreceives a new supply of uncalibrated thermometers.

FIRST SCANNING AND INKING STATION D The first scanning and inkingstation D is illustrated in FIG. 3, which illustrates in more detailedfrom the system shown schematically in FIG. 1. Corresponding componentsin FIG. 3 are further identified, where there is correspondence, withthe reference numerals used in FIG. 1. As shown in FIG. 3, thethermometer 16 is carried by a holder 88 which in turn is secured to theconveyor. The reflecting mirror 18 is mounted on a mirror holder 90,which in turn is secured to a slide or carrier 92. Carrier 92 isvertically movable along a guide 94 fixedly secured to a support post96. The photodetector 26 is mounted on the upper portion of carrier 92and is oriented so that its optical axis is directed along the axis ofthe reflected laser beam; that is, the beam from laser 62 (10) reflectedfrom mirror 18 and then from the mercury column in the thermometer. Alsomounted on carrier 92 and movable along therewith is the inker 32. Asshown in FIG. 3, the central longitudinal axis of inker 32 lies alongthe axis of the beam reflected from mirror 18 onto the mercury column inthe thermometer.

The reflected laser beam is scanned over the mercury column in thethermometer each time a new thermometer is indexed into position instation D by incrementally and vertically moving the carrier 92 to varythe vertical position of the mirror. As herein shown, vertical movementof the carrier with respect to the thermometer is produced by a steppingmotor 98 mounted on support post 96 and having an output shaft coupledto a ball screw 100. The latter in turn is coupled at its upper end tocarrier 92. The operation of stepping motor 98 in response to a drivesignal produces incremental rotational motion of the ball screw, whichin turn is converted to incremental vertical motion of the carrier.

As has been described above with reference to FIG. 1, when detector 26senses the discontinuity at the upper meniscus of the mercury column, itproduces a signal which operates in a manner more completely describedbelow with reference to FIG. 8 to temporarily disable motor 98 and'thusmaintain the carrier and laser beam at a fixed vertical position.Shortly thereafter, a signal is produced which actuates a solenoid tocause inker 32 to spray a quantity of ink onto the thermometer casing atthe location of the upper level of the column, to thereby form the inkedline at the first temperature reference level. After the completion ofthe inking operation, the carrier is returned by the motor to itsinitial rest position and a new thermometer is indexed into position forscanning and markmg.

SECOND SCANNING STATION F The second scanning station F at which thethermometer is again scanned by a laser beam after the mercury columnhas risen to its second elevated reference level as a result of itsimmersion in the controlled bath at station E, operates in a mannersimilar to that of the first scanning station. At station F a beam fromlaser is caused to be reflected from an inclined mirror 102 mounted on aholder 104 which in turn is mounted on a carrier or slide 106'. Slide106, which is free to move vertically within a guide 108 mounted on asupport post 110, also carries a photodetector 112 which is positionedas shown in FIG. 4 so that its optical axis lies substantially along theaxis of the beam reflected from the mercury column of the thermometer.

A rod 114 is supported by and extends downwardly from slide 106-and hasa lower portion 116 that passes between a light beam produced by a lightsource 118 and a light detector 120 mounted on support post 110 for mostpositions of the slide. The lower end of slide 106 is couplled by auniversal joint 122 to a shaft 124. The latter in turn is. secured to apin 126 which is eccentrically mounted on a wheel or disc 128. Wheel 128is in turn fastened on a shaft 130 of a drive motor 132.

The other end of shaft 130 carries a Geneva drive 134 which is coupledby a belt 136 to a drive wheel 138. Drive wheel 138 is in turn fast onone end of a shaft 140 journalled in a shaft housing 142 supported on amounting bracket 144. The other end of shaft 140 is secured to asprocket wheel 146 which engages the chain conveyor 34.

The operation of Geneva drive 134 by the motor 132 and the coupling ofdrive 134 to the sprocket wheel produce an incremental longitudinalmovement of the chain conveyor between loading station A and theunloading and classifying station B. At the same time, the operation ofthe eccentrically mounted shaft 124 causes periodic verticalreciprocation of slide 106 and thus causes the laser beam toperiodically 'scan over the mercury column in the thermometer inresponse to the positioning of a new thermometer in scanning station F.Since both shaft 106 and Geneva drive 134 are both coupled to the samedrive motor, synchronization between conveyor indexing and beam scanningis achieved. A rack section 148 is fixed along one edge of slide 106 anda pinion 150 engages rack section 148 and a gear member (not shown) of ashaft encoder 152 fixedly mounted on post 110. The verticalreciprocatory movement of slide 106 is, by virtue of this arrangement,converted to rotary motion of the gear member in the shaft encoder. As aresult, the encoder produces a series of pulses proportional to theextent of vertical movement of slide 106 for reasons which will bedescribed below.

At the time of a new thermometer is indexed into position at station F,the operation of the eccentric causes mirror-carrying slide 106 to bemoved to its maximum vertical position along with mirror 102 and rod114, until the latter no longer interrupts the light beam from source118. This causes detector 120 to produce a signal indicating thebeginning of a new scanning operation for the new thermometer. At thistime the operation of the eccentric causes slide 106 to begin itsdownward travel, causing the laser beam to scan the thermometer from itsupper section where there is no mercury in the capillary bore until thediscontinuity at the upper level of the mercury column is detected bydetector'112 in the manner described above. The detector 112 thereuponproduces a first or mercury signal which is applied to a logic circuitdescribed more completely with respect to FIG. 9. Slide 106 continues tomove downwardly and the beam continues to scan the mercury column untilthe reflection from the ink line produced at the first scanning stationat the first reference level is detected. Detector 112 thereuponproduces a first or mercury signal which is applied to a logic circuitdescribed more completely with respect to FIG. 9. Slide 106 continues tomove downwardly and the beam continues to scan the mercury column untilthe reflection from the ink line produced at the first scanning stationat the first reference level is detected. Detector 112 thereuponproduces a second or ink line signal which is employed along with thefirst detection signal in the logic circuit of FIG. 9 to produce ananalog signal in the form of a series of output pulses from encoder 150.The number of those pulses is representative of the distance between thetwo reference levels. These pulses are converted, as described morecompletely below with respect to FIGS. 9 and 10, to establish a binaryclassification designation for the thermometer which relates in apredetermined manner to that distance.

UNLOADING AND CLASSIFICATION STATION B After the thermometers have leftthe second scanning station, they are transferred to unloading andsorting station B, which is shown schematically in FIG. 5. At station Bthe thermometers are incrementally carried by the conveyor chain over aplurality of classification chutes 154 which communicate at their lowerend with a corresponding plurality of removable bins or compartments156. A corresponding plurality of solenoids 158 (FIG. 6) are positionedalong the conveyor chain, one solenoid being arranged above each of theclassification chutes. The axis of the solenoids is substantially normalto the direction of movement of the conveyor past the open upper ends ofthe chutes.

As described more completely with reference to FIGS. 7 and 10, when athermometer is positioned over the chute corresponding to its categoryas determined at scanning station F, the solenoid at that chute isactuated and the thermometer is released from its holder on the conveyorand falls down the classification chute into the designated receptaclelocated at the lower end of that chute. The position of thermometerrelease from the conveyor belt is a function of the number of encoderpulses derived at the second scanning station, and the thermometers-arethus automatically calibrated and classified according to thetemperature levels established and sensed at the first and secondscanning stations.

FIG. 7 illustrates the manner in which the thermometers may be loadedonto the conveyor either manually or automatically at loading station A,and carried on the chain until their release at station B. Thethermometer holders each comprise a fixed support member or nest 162,and a movable finger or claw member 164 pivotedly mounted on member 162by a pin 166. Claw members 164 each comprise a release clip 168. Aspring is secured to members 162 and 164 and is bent about a pin 166.

Prior to the loading of the thermometers onto the conveyor, the hooks ofmembers 164 are biased away from the arcuate surface of members 162 bymeans of a depression bar 172 fixedly positioned at the loading stationand acting against the release clips of members 164. A space 174 isdefined between members 162 and 164 as shown in the two lefthand holdersin FIG. 7, which allows the placement therein of an uncalibratedthermometer. As soon as the conveyor moves past the location ofdepressing bar 172, spring 170 urges member 164 to the position shown inthe two right-hand holders in FIG. 7, causing the claw member 164 andthe nest 162 to securely grasp the thermometer therebetween.

A typical solenoid control release mechanism at the unloading station isshown in FIG. 6 in which solenoid 158 is shown coupled to a release arm176 which, when inoperative, is spaced from the release clips 168 of theclaw members 164. When the solenoid is activated, arm 176 is moved intocontact with release clips 168 to pivot claw member 164 away from thenext 162, and thereby cause the thermometer to be released from theholder and fall from the conveyor into the desired classification chute.

FIG. 8 illustrates in block form the logic and control circuitryemployed in the operation of the first scanning station D. The output ofdetector 26 is coupled to an amplifier and shaper 178 the output ofwhich is coupled to one input of an AND gate 180. The other input togate 180 is a signal derived from the conveyor indexing mechanismindicating that the conveyor is at a rest position, i.e., that it is notat that time indexing.

When gate 180 receives at its two inputs signals indicating that ameniscus is detected and that the belt is at rest, it produces an outputsignal which is applied as one input to an AND gate 182. That gate alsoreceives at its other input a signal delayed in delay 184 derived from alimit switch (not shown) at the lowest point to which slide 92 travelsto indicate that the slide 92 is reset for a beam scanning operation ona newly indexed thermometer.

When both signals are received at the inputs of gate 182 it produces anoutput signal which is in turn applied to one input of an AND gate 186,the other input of which receives a train of timing signals from a clockgenerator 188. When both signals are present at the inputs of gate 186,it produces an output signal which is applied to a stop forward drivecircuit 190, such as a relay, to thereupon disable motor 98 andtemporarily stop the further vertical movement of carrier 92.

The output of gate 186 is also applied to one input of an AND gate 192,the other input to which receives the output of gate 182 delayed by adelay 194. When both input signals are present at gate 192, it producesan output signal which actuates the inker solenoid (not shown) to causethe inker 32 to produce the reference marker on the thermometer casingas described above. The delay between the stopping of the scan motor andthe operation of the inker by delay 194 permits the thermometer positionto stabilize prior to the inking operation.

The output of gate 192 is also applied to one input of an AND gate 196which receives at its other input the undelayed output of gate 182. Whenboth signals are present at the inputs of gate 196, indicating that themotor is at rest and the inker is actuated, gate 196 produces an outputsignal which is applied to one input of an AND gate 198, the other inputof which receives synchronizing signals from clock generator 188.

When signals are present at each input of gate 188, it produces onoutput signal which is applied to and actuates a reverse drive circuit200. Circuit 200 when actuated causes motor 98 to be returned to itsuppermost position in preparation for a new scanning operation on anewly indexed thermometer.

FIG. 9 illustrates the logic and binary conversion circuitry associatedwith the operation of scanning station F. An AND gate 202 receives asignal at one input from detector 120 indicating that the conveyor isstopped, to wit, not indexing, and at its other input it receives theoutput pulses from shaft encoder 152. When both signals are present,gate 202 produces an output signal which is applied to one input of anAND gate 204.

When detector 112 detects the meniscus in the mercury column it producesa signal as noted above, which signal is stored in a mercury leveldetect memory 206 and applied to the other input of gate 204. Upon thecoincidence of signals at the inputs of gate 204, pulses are produced atthe output of the gate. Those pulses are coupled to a 12:1 counter 208in which the number of encoder pulses is divided by twelve. The outputpulses of counter 208 are applied to one input of an AND gate 210. Thelevel detector signal is also applied to one input of an AND gate 212.Each time carrier 106 completes one vertical movement in response to acomplete revolution of wheel 128, detector 120 produces a signal whichis applied to a memory 214.

The output of memory 214 is coupled to the other input of gate 212 whichproduces at the coincidence of its input signals an output signalindicating that detector 112 has detected the reflection of the laserbeam from the inked line. That signal is stored in an ink-line memory216. The output of memory 216 is applied to an inverted input of gate210. That gate thus permits the encoder pulses to pass only in theperiod between the detection of the upper mercury level (the signal fromgate 204) and the detection of the inked line (the signal from gate212). The number of output pulses from gate 210 thus reflects thedistance between the two reference levels respectively detected atscanning stations D and F.

Those pulses are applied to the input of a counter 218, which receivesthe analog pulse train and converts the number of these pulses into afive-bit parallel work. That word defines in binary form one of 31categories based on the spacing between the two reference levels. In theembodiment of the invention herein described, a count of greater than 82or less than 52 is considered to be unacceptable for use andcalibration. When this occurs, counter 218 also provides an over 82signal and an under 52 signal. The former is applied to one input of anOR gate 220 to thereby produce a reject signal.

The revolution pulse and the output of memory 214 are appliedrespectively to the two inputs of an AND gate 222, the output of whichis in turn coupled to one input of an AND gate 224. The other invertedinput to gate 224 is received from the ink line memory 216 so that theoutput of gate 224 when present indicates a complete scan and an absenceof an ink line. The output of gate 224 is applied at line 226 and toanother input of OR gate 220. y

The under 52 signal from counter 218 and the ink line signal from memory216 are both applied to the two inputs of an AND gate 228, the output ofwhich is applied to a third output of OR gate 220. The outputs of gate202 and memory 216 are applied respectively to the two inputs of an ANDgate 230, the output of which is applied to one input of an AND gate232. The other input to gate 232 is the revolution pulse derived fromdetector 120. The output signal from gate 232 indicates that the encoderis producing output pulses, that the ink line is sensed, and that theslide has gone through a complete scanning cycle. That signal is appliedto a counter and comparator 234. When the latter counts a number ofencoder pulses less than a predetermined number (e.g. 313 in an actualembodiment of the invention), the signal from gate 232 is allowed totransfer a signal to another input of OR gate 220 which in turn producesa reject signal. This control reject feature is provided to ensure thatthe mercury signal detected when the beam is scanned over the meniscusis in fact a true meniscus rather than the top of the thermometer casingwhich may produce a similar reflection of the beam. The latter situationmay arise when a relatively short thermometer is indexed into the secondscanning station. As soon as counter 234 counts more than thepredetermined minimum number of encoder pulses, its logic inhibits thegate 232 signal from OR gate 220 and thus permits the counting of theencoder pulses in counter 218.

For any input at OR gate 220 a reject signal is provided indicating athermometer in which the distance between the reference point is outsidean acceptable value, or an improper operation of the encoder or theinking and scanning stations.

FIGS. 10 and 11 illustrate schematically the logic circuitry associatedwith the classifying and unloading operation that takes place at stationE. The 5-bit parallel classification word from counter 210 and thereject signal from gate 220, if present, are applied respectively to theinputs of 8-bit shift registers 236-246. The outputs of shift registers236-246 are respectively applied to the inputs of 3-bit shift registers248-258. The shift inputs of all shift registers receive shiftingsignals from detector in scanning station F indicating an indexingoperation on the thermometers. The series-connected shift-registers thusprovide an eleven-step delay between the scanning operation at station Fand the arrival of the thermometer at the sorting and unloading stationB.

The delayed S-bit word, representing which one of the 31 categories thethermometer is assigned by virtue of the distance between the tworeference levels, is applied to a category decoder and logic circuit 259(FIG. 10) which also receives conveyor indexing signals indicating theposition of the thermometer in the sorting station. When a coincidenceis sensed between the assigned category binary number and thethermometer position at station B, e.g., category and position codenumber 13, a signal is produced and applied to the solenoid drivecircuit 260 which is coupled to the solenoid located at thecorresponding (number 13) classification chute. In this manner, thethermometer is unloaded into that receptacle located at the lower end ofthe category 13 chute specifically assigned to receive all thermometersfalling into that category.

On the other hand, if a reject signal is received at decoderlogiccircuit 259 for any of the reasons listed above, only the rejectsolenoid is actuated and the thermometer is unloaded from the conveyorby operation of the reject solenoid when it arrives at the dischargechute.

FIG. 11 illustrates a possible modification of the first scanningstation which permits the use of a single laser beam to simultaneouslyscan two continuously moving rows of thermometers to detect the upperlevel of the mercury column in a manner similar to that described above.As therein shown, the laser beam is caused to be incident on a beamsplitter 262 which directs a portion of the laser beam onto a pair ofmirrors 264 and 266 which can be moved vertically with respect to thethermometers to achieve beam scanning over the mercury column. Thetransmission characteristics of the laser beam at the mercury columnsare detected at detectors 268 and 270 to produce signals which may beemployed in a continuous calibrating and classifying operation in amanner similar to that described above.

The system of the invention thus provides means for automaticallycalibrating and classifying instruments such as clinical thermometers ina continuous manner while still achieving precision of calibration. Thesystem of the invention operates in a relatively high speed manner andproduces results which are repeatable over long periods of use involvinga great many thermometers. Precision of calibration is achieved in thesystem of the invention by the use of a narrow laser beam which producesa characteristic change in reflectivity or transmissivity upon thesensing of the upper level or meniscus of the mercury column within thethermometer.

While the system has been herein described with particular reference tothe calibration and classification of clinical thermometers, it may alsobe utilized to equal advantage with other thermometers such as outdooror indoor weather thermometers, or in other measuring instruments suchas barometers or the like, in which a medium is caused to move within anenclosed capillary bore in response to the level of a sensed ex ternalparameter.

Moreover, while in the embodiments shown the detector is located on thecarrier at a location above the mirror, it could also be carried on thesame plane as the mirror and positioned with its optical axis along theaxis of the reflected laser beam. While the forming of the ink line atthe first reference level is achieved in the described embodiment by anink spraying device, that line may also be formed by other means such ascontacting the thermometer casing with an impregnated felt member. Theink line could also, if desired, be formed at the upper reference levelas well as the first or lower reference level. The thermometer releasemechanism could also include a hydraulic or pneumatic solenoid as wellas the electrical solenoid as herein described.

Thus while the invention has been herein described with particularreference to several of its embodiments, it will be understood thatvariations and modifications may be made therein, all without departingfrom the spirit and scope of the invention.

We claim:

1. A system for automatically calibrating an instrument of the typehaving a medium extending axially within a relatively narrow column inresponse to the value of a sensed external parameter, said systemcomprising means for establishing a first reference parameter at theinstrument to thereby cause the medium to rise in the column to a firstreference level corresponding to the value of said first referenceparameter, first means for scanning a first narrow beam of light overthe instrument, first means located in the optical path of said lightbeam for detecting when said light beam is directed at said firstreference level, means spaced from said parameter establishing means forestablishing a second reference parameter different from said firstreference parameter at the instrument to cause the medium to rise to asecond reference level in the column, second means for scanning a secondnarrow light beam over the instrument, and second means for detectingwhen said second beam is directed at the medium at said second referencelevel.

2. The system of claim 1, further comprising means coupled to said firstand second detecting means for respectively deactivating said first andsecond beam scanning means when said beam is directed at said first andsecond reference levels.

3. The system of claim 2, further comprising first and second indiciaforming means respectively coupled to said first and second scanningmeans and movable along therewith, and means coupled to said first andsecond detecting means for respectively activating said first and secondindicia forming means to thereby respectively establish indications onsaid instrument at said first and second reference levels.

4. The system of claim 1, further comprising means coupled to saidsecond scanning means for sensing the distance along the column betweensaid first and second reference levels.

5. The system of claim 4 in which said first and second scanning meansrespectively comprise first and second sources of laser beams, saidlaser beams respectively defining said first and second narrow lightbeams, a carrier, first and second reflecting means receiving said laserbeams thereon and secured to said carrier, and means for producingrelative motion between said carrier and the instrument.

6. The system of claim 5, further comprising means for deriving a firstsignal corresponding to the distance between said first and secondtemperature levels, and an instrument release station having a pluralityof classifying units, means for transferring the instrument from saidsecond parameter establishing means to said release station, and meansresponsive to said distance signal and to the position of the instrumentfor releasing the latter at said release station at a preselected one ofsaid classifying units.

7. The system of claim 6, m which said second scanning means comprises asecond carrier carrying said second detecting means, and secondreflecting means carried on said second carrier, said distance sensingmeans comprising means for producing a signal relative to thedisplacement of said second carrier between said first and secondreference levels.

8. The system of claim 7, in which said distance signal producing meanscomprises encoder means coupled to said second carrier for producing anumber of pulses proportional to the distance traveled by said secondcarrier, and further comprising pulse counting means, means forbeginning the counting of said pulses in response to the detection ofsaid second reference level, and means for ending the counting of saidpulses in response to the detection of said indication formed on theinstrument by said indicia forming means.

9. The system of claim 1, further comprising first and second indiciaforming means respectively coupled to said first and second scanningmeans and movable along therewith, and means coupled to said first andsecond detecting means for respectively activating said first and secondindicia forming means to thereby establish indications on saidinstrument at said first and second reference levels.

10. The system of claim 9, further comprising means coupled to saidsecond scanning means for sensing the distance along the column betweensaid first and second reference levels.

11. The system of claim 10, further comprising means for deriving afirst signal corresponding to the distance between said first and secondtemperature levels, an instrument release station having a plurality ofclassifying units, means for transferring the instrument from saidsecond parameter establishing means to said release station, and meansresponsive to said distance signal and to the position of the instrumentfor releasing the latter at said release station at a preselected one ofsaid classifying units.

12. The system of claim 10, in which said second scanning meanscomprises a second carrier carrying said second detecting means, andsecond reflecting means carried on said second carrier, said distancesensing means comprising means for producing a signal relative to thedisplacement of said second carrier between said first and secondreference levels.

13. The system of claim 10, in which said distance signal producingmeans comprises encoder means coupled to said second carrier forproducing a number of pulses proportional to the distance traveled bysaid second carrier, and further comprising pulse counting means, meansfor beginning the counting of said pulses in response to the detectionof said second reference level, and means for ending the counting ofsaid pulses in response to the detection of said indication formed onthe instrument by said indicia forming means.

1. A system for automatically calibrating an instrument of the typehaving a medium extending axially within a relatively narrow column inresponse to the value of a sensed external parameter, said systemcomprising means for establishing a first reference parameter at theinstrument to thereby cause the medium to rise in the column to a firstreference level corresponding to the value of said first referenceparameter, first means for scanning a first narrow beam of light overthe instrument, first means located in the optical path of said lightbeam for detecting when said light beam is directed at said firstreference level, means spaced from said parameter establishing means forestablishing a second reference parameter different from said firstreference parameter at the instrument to cause the medium to rise to asecond reference level in the column, second means for scanning a secondnarrow light beam over the instrument, and second means for detectingwhen said second beam is directed at the medium at said second referencelevel.
 2. The system of claim 1, further comprising means coupled tosaid first and second detecting means for respectively deactivating saidfirst and second beam scanning means when said beam is directed at saidfirst and second reference levels.
 3. The system of claim 2, furthercomprising first and second indicia forming means respectively coupledto said first and second scanning means and movable along therewith, andmeans coupled to said first and second detecting means for respectivelyactivating said first and second indicia forming means to therebyrespectively establish indications on said instrument at said first andsecond reference levels.
 4. The system of claim 1, further comprisingmeans coupled to said second scanning means for sensing the distancealong the column between said first and second reference levels.
 5. Thesystem of claim 4 in which said first and second scanning meansrespectively comprise first and second sources of laser beams, saidlaser beams respectively defining said first and second narrow lightbeams, a carrier, first and second reflecting means receiving said laserbeams thereon and secured to said carrier, and means for producingrelative motion between said carrier and the instrument.
 6. The systemof claim 5, further comprising means for deriving a first signalcorresponding to the distance between said first and second temperaturelevels, and an instrument release station having a plurality ofclassifying units, means for transferring the instrument from saidsecond parameter establishing means to said release station, and meansresponsive to said distance signal and to the position of the instrumentfor releasing the latter at said release station at a preselected one ofsaid classifying units.
 7. The system of claim 6, in which said secondscanning means comprises a second carrier carrying said second detectingmeans, and second reflecting means carried on said second carrier, saiddistance sensing means comprising means for producing a signal relativeto the displacement of said second carrier between said first and secondreference levels.
 8. The system of claim 7, in which said distancesignal producing means comprises encoder means coupled to said secondcarrier for producing a number of pulses proportional to the distancetraveled by said second carrier, and further comprising pulse countingmeans, means for beginning the counting of said pulses in response tothe detection of said second reference level, and means for ending thecounting of said pulses in response to the detection of said indicationformed on the instrument by said indicia forming means.
 9. The system ofclaim 1, further comprising first and second indicia forming meansrespectively coupled to said first and second scanning means and movablealong therewith, and means coupled to said first and second detectingmeans for respectively activating said first and second indicia formingmeans to thereby establish indications on said instrument at said firstand second reference levels.
 10. The system of claim 9, furthercomprising means coupled to said second scanning means for sensing thedistance along the column between said first and second referencelevels.
 11. The system of claim 10, further comprising means forderiving a first signal corresponding to the distance between said firstand second temperature levels, an instrument release station having aplurality of classifying units, means for transferring the instrumentfrom said second parameter establishing means to said release station,and means responsive to said distance signal and to the position of theinstrument for releasing the latter at said release station at apreselected one of said classifying units.
 12. The system of claim 10,in which said second scanning means comprises a second carrier carryingsaid second detecting means, and second reflecting means carried on saidsecond carrier, said distance sensing means comprising means forproducing a signal relative to the displacement of said second carrierbetween said first and second reference levels.
 13. The system of claim10, in which said distance signal producing means comprises encodermeans coupled to said second carrier for producing a number of pulsesproportional to the distance traveled by said second carrier, andfurther comprising pulse counting means, means for beginning thecounting of said pulses in response to the detection of said secondreference level, and means for ending the counting of said pulses inresponse to the detection of said indication formed on the instrument bysaid indicia forming means.